This invention relates in general to communication systems, and more specifically to a method and apparatus for effecting a seamless handoff of packet data communication from one IP connection to another.
Communications systems are known and continue to evolve rapidly as is quite evident in wireless communications systems. Systems have and are being deployed that allow packet data enabled mobile stations access to packet data networks such as the Internet or internet like networks that utilize IP addresses and various packet data transport protocols such as internet protocol (IP), transport control protocol (TCP), Universal Datagram Protocol (UDP) and more recently stream control transmission protocol (SCTP). Many second and third generation cellular and cellular like systems, such as GPRS (general packet radio service), CDMA (code division multiple access) 2000, Wideband CDMA, UMTS (Universal mobile telecommunications service) rely on or support such packet data protocols. Such cellular systems are typically arranged and constructed to provide handoff for a communications from one cellular fixed point to another same cellular fixed point more or less transparent to or with little or no indication to a user of the system.
Other communications systems are gaining popularity and these may be characterized as small or local area systems, often wireless, that provide services to users, typically after proper authorization and authentication procedures have been successful. Such wireless systems include ones based on or designed around IEEE 802.11, for example. Most of these systems are designed to be low cost and largely intended to eliminate hooking up wires and cables. Thus these systems for the most part have not dealt with mobility issues, such as handing off a communications from one fixed or access point to another in the midst of a communications much less accepting or initiating handoffs from and to cellular or cellular like systems. Some 802.11 systems do have the ability to pick up a communication that has been dropped by one fixed point at another fixed point provided the fixed points are part of the same subnet, referred to as a basic services set or BSS in 802.11 systems, however this can take several seconds and is not suitable for handling mobile users with real-time or time critical needs.
Clearly a need exists for methods and apparatus for effecting a handoff of time critical communications from one IP connection to another. Preferably this will be transparent to the systems, network operators, and users and support legacy equipment and applications using TCP/UDP packet data.